In order to meet exhaust fluid emission standards, the exhaust emitted from internal combustion engines is treated prior to emission into the atmosphere. Exhaust fluids may be routed through at least one exhaust emission treatment device disposed in fluid communication with the exhaust outlet system of the engine, wherein the exhaust fluids are treated by reactions with a catalyst composition deposited on a porous support material. Examples of exhaust emission treatment devices include catalytic converters, catalytic absorbers, diesel particulate traps, and the like. The exhaust fluid generally contains undesirable emission components including carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx), sulfates (SO3) and particulates. In particular, sulfur compounds deactivate precious metals, and the temperature needed for precious metal regeneration exceeds exhaust temperatures. As a means of simultaneously removing the objectionable CO, HC, NOx and SOx components, various catalyst compositions have been developed.
However, a need remains in the art for an improved catalyst compositions used in a catalytic exhaust treatment device.